The invention relates to a coupling member permitting the transmission of a movement without off-centering or torque loss in both directions when the receiver member is moved by the motor member and the transmission of a movement without off-centering or torque loss in a single direction when the functions of the motor and receiver members are reversed. Thus, the transmission of the movement of the receiver member to the motor member is locked after rotating the receiver member by a fraction of a turn. Unlocking can be obtained either by the movement of the motor member by the receiver member in the single operating direction, or by the control of the movement in one or the other direction by the motor member.
A large number of devices for transmitting a rotary movement between a motor member and a receiver member are known. These devices are more particularly used in the control of the control rods of nuclear reactors. French Pat. No. 78 22 253 filed on July 27th 1978 in the name of the Commissariat a l'Energie Atomique and entitled "Device for controlling a control rod of a nuclear reactor provided with safety means preventing ejection and turning over" describes a device of this type. It comprises a mechanism for controlling the translation of the control rod located in a tight enclosure integral with the reactor vessel cover, means for preventing the ejection of the control rod and finally means for controlling the anti-ejection means which are sensitive to an external influence urging the control rod out of the reactor core.
In reactors of this type, the power of the nuclear boiler is regulated by introducing control rods to a greater or lesser depth into the reactor core, having as the main characteristic a high neutron-absorbing power. The control device of these control rods must not only permit their lowering and raising, but also their rapid drop in the case of an increase in reactivity.
Water reactors are also used for the propulsion of ships. Thus, they are subject to the possibility of being turned over, which in certain circumstances can lead to the control rods being extracted from the reactor core, which can lead to damage and injury.
The control rods can also be extracted if the sealing of the enclosure containing the control rod control mechanism is broken, because this would lead to a rapid depressurization of the enclosure. This depressurization would lead to a pressure difference between the interior of the enclosure and the interior of the reactor vessel. This pressure difference would lead to a considerable pressure on the control rod and would tend to eject it from the reactor core. Thus, devices are provided for preventing the ejection of control rods from water reactors in the case of a depressurization of the enclosure containing the control rod control mechanism, or in the case of the reactor being turned over when it is on board a ship.